STUDIES OF FUNCTIONS INVOLVED IN GENETIC RECOMBINATION

这个项目目前的重点是了解DNA是如何 超螺旋由DNA促旋酶和相关酶引起， 研究DNA超螺旋对细菌基因表达的影响。 这些是最近的一些结果： ATP类似物（β，γ-亚氨基）ATP的极慢结合 在ATP的存在下，DNA促旋酶的转化大大加速。 因此 矛盾的是，ATP可以帮助类似物阻断ATP结合位点， 抑制酶。 DNA超螺旋对细菌转录的影响已经被证实， 进一步研究。 在由DNA松弛诱导的启动子中， 第一转录区的结构被证明是重要的; 当DNA超螺旋时，许多转录物过早终止， 而全长转录物在松弛的DNA上形成。 对嗜热菌的反向DNA旋转酶的实验 表明，与所有其他拓扑异构酶测试，这种酶只能 在一个方向上改变超螺旋（朝向正超螺旋）。 逆转录酶是ATP依赖性的，但可以与一个显着的 低浓度的ATP。

The present focus of this project is to understand how DNA supercoiling is brought about by DNA gyrase and related enzymes, and to study the effects of DNA supercoiling on bacterial gene expression. These are some recent results: The extremely slow binding of the ATP analog (beta, gamma-imido) ATP to DNA gyrase is greatly accelerated in the presence of ATP. Thus paradoxically ATP can help the analog to block ATP binding sites and inhibit the enzyme. The effect of DNA supercoiling on bacterial transcription has been further studied. In a promoter that is induced by DNA relaxation, the structure of the first transcribed region turns out to be important; when the DNA is supercoiled, many transcripts terminate prematurely, while full-length transcripts are formed on relaxed DNA. Experiments on the reverse DNA gyrase of thermophilic bacteria have shown that, unlike all other topoisomerases tested, this enzyme can only change supercoiling in one direction (toward positive supercoiling). Reverse gyrase is ATP-dependent, but can function with a remarkably low concentration of ATP.